Newbie trying to understand rolling resistance tests, requesting assistance

77 replies · 1,980 views

John Z
174 posts
#61Feb 17, 2023, 10:50 AM
Alagrav wrote:

I'm not expecting science to provide an absolute answer in terms of gravel tire or pressure choice. Terrain varies too much for a precise scientific approach. Look at, for example, cyclocross. Some pretty big names contesting Worlds recently. Yet tire choice for a course, and tire pressure, remains an art in that sport. And when it doesn't "feel" right to the pros, they'll pit and get a bike with different tires or pressures. There are no pits in gravel races, so you gotta take your best guess and ride it.

Thanks for starting the tread. Some folks that appear very wise and informative have taken the time to post here and I've appreciated greatly their input.

Again, I think the opposite. There is no art to picking a tire, tire width and tire pressure. And science certainly has shown that "feel" is often incorrect.
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thumper88
198 posts
#62Feb 17, 2023, 11:46 AMedited
John wrote:

Again, I think the opposite. There is no art to picking a tire, tire width and tire pressure. And science certainly has shown that "feel" is often incorrect.

I think I kind of agree with both of you. Your concerns about “feel” are absolutely true and have been proven over and over.
But since the science is only getting us some percentage of the way to the answer, and every course is a different mix of pavement and gravel type and mud or no mud -- even the same course on different days, weeks or years -- and there are constantly new and untested or little-tested tires coming on the scene?
....the rest of what we put in the hopper to pick a tire, tire size and pressure could be called art.
That doesn’t imply -- at least for me -- that I’m a genius artist making the right choice. I may not be. I may be pretty far off in fact.
But it means I’m trying my best, with the information I do have, plus my experience etc.
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John Z
174 posts
#63Feb 17, 2023, 12:29 PMedited
thumper88 wrote:

I think I kind of agree with both of you. Your concerns about “feel” are absolutely true and have been proven over and over.
But since the science is only getting us some percentage of the way to the answer, and every course is a different mix of pavement and gravel type and mud or no mud -- even the same course on different days, weeks or years -- and there are constantly new and untested or little-tested tires coming on the scene?
....the rest of what we put in the hopper to pick a tire, tire size and pressure could be called art.
That doesn’t imply -- at least for me -- that I’m a genius artist making the right choice. I may not be. I may be pretty far off in fact.
But it means I’m trying my best, with the information I do have, plus my experience etc.

I suppose you could call it an "art" to take the best available scientific data then making the choice of a specific tire, width and pressure based upon conditions. But I honestly think many are obsessing over the minutia, even for example concerns for new, untested tires, as tire technology is pretty advanced now and any future gains in capability is going to be marginal. Even then, your worst scenario is a few hundred dollars.

So, you want a "fast' gravel tire, it is a simple process. Science says that for equi-pressure, wider tires have lower rolling resistance, this especially true as conditions get rougher. Thus, create a list of the widest tires that your bike, for me that is 40mm:

Next, decide how much tread is required, if any. I want a knob of at least 1mm, so that reduces the selection by 5:

Now, the question becomes how much "speed" do I want to sacrifice for knob height? Let's say I want more "speed":

That leaves me with three tires meeting my criteria. Since I am willing to sacrifice a little grip for better puncture resistance, I go with the Terra Speeds. It's not rocket science.
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thumper88
198 posts
#64Feb 17, 2023, 12:56 PM
John wrote:

I suppose you could call it an "art" to take the best available scientific data then making the choice of a specific tire, width and pressure based upon conditions. But I honestly think many are obsessing over the minutia, even for example concerns for new, untested tires, as tire technology is pretty advanced now and any future gains in capability is going to be marginal. Even then, your worst scenario is a few hundred dollars.

So, you want a "fast' gravel tire, it is a simple process. Science says that for equi-pressure, wider tires have lower rolling resistance, this especially true as conditions get rougher. Thus, create a list of the widest tires that your bike, for me that is 40mm:

Next, decide how much tread is required, if any. I want a knob of at least 1mm, so that reduces the selection by 5:

Now, the question becomes how much "speed" do I want to sacrifice for knob height? Let's say I want more "speed":

That leaves me with three tires meeting my criteria. Since I am willing to sacrifice a little grip for better puncture resistance, I go with the Terra Speeds. It's not rocket science.

All good. An elegant and rational process.
For my style of riding I don’t care much about tread. I’m not going to rail fast sweepers... trying hard not to die was why I left road racing.
I just want enough grip to get up 20 percent slightly loose hills.
So I looked at the five or six fast tires and ... the RS in 45mm works for me. I’ve pretty much decided there’s nothing to be gained by going smaller except on the very hardest of hardback and pavement. And the RS -- other than not even find knobs up the middle .... is pretty close to the 45mm Terra Speed Ive been waiting for and Conti seems in no hurry to produce.
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thumper88
198 posts
#65Feb 17, 2023, 12:58 PM
And yes it’s true that tire tech has gotten ripe enough that there’s probably no particularly significant gain to expect from any new model that’s unveiled. But... I do want some 45mm conties.
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Alagrav
18 posts
#66Feb 17, 2023, 1:00 PM
I'm with you on the science part. You list some science based steps in your process, but then you say:

Next, decide how much tread is required, if any. I want a knob of at least 1mm, so that reduces the selection by 5:

and:

Now, the question becomes how much "speed" do I want to sacrifice for knob height? Let's say I want more "speed":

Where's the chart of data and test results that tells you how to decide how much tread is required for the current course conditions? Where is the online calculator that calculates how much knob height will help on the sections of the course where traction is needed
and how much it will slow you on sections where you could ride with no loss of speed on slicks?

The art comes with matching what we know about tire speed, tread, and puncture resistance) with our best guess of course conditions.
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phrantic09
12 posts
#67Feb 17, 2023, 2:46 PM
John wrote:

I have the exact opposite opinion of BRR and I am a premium member. Regarding the Tufos, that is a Tufo question, not a BRR one.

I guess what I was getting at is that the fact that they test the same could be indicative of some flaw in the procedure. I’m a premium member as well and I generally look at their reviews for making tire purchases, but this one has me stumped about which tire to actually get
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John Z
174 posts
#68Feb 17, 2023, 4:03 PM
Alagrav wrote:

Where's the chart of data and test results that tells you how to decide how much tread is required for the current course conditions? Where is the online calculator that calculates how much knob height will help on the sections of the course where traction is needed
and how much it will slow you on sections where you could ride with no loss of speed on slicks?

The art comes with matching what we know about tire speed, tread, and puncture resistance) with our best guess of course conditions.

Testing grip on loose surfaces is virtually impossible and in another thread, from earlier in the year, a member made a valid point that treads on most gravel tires have a greater psychological value than practical. Even if this is the case, a three watt difference per tire is not going to make or break you.

I actually ride with a Terra Speed in the front and a Terra Trail in the rear. Why? I am not 100% sure that their knobbies don't have a positive value in loose conditions, and Terra Speeds seem to wear a little faster than Terra Trails.

As for pressure, best to err a bit on the low side.
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John Z
174 posts
#69Feb 17, 2023, 4:05 PM
phrantic09 wrote:

I guess what I was getting at is that the fact that they test the same could be indicative of some flaw in the procedure. I’m a premium member as well and I generally look at their reviews for making tire purchases, but this one has me stumped about which tire to actually get

Could be that they have different compounds? Or, since the center knob height differs by only 0.2mm, its not enough to matter?
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wheelmonkey
8 posts
#70Feb 17, 2023, 11:54 PM
Alagrav wrote:

Really? Who was running 120-200 psi? I started racing triathlon in 1989, some crits and road races in 2000s, cyclocross in 2006, and gravel three years ago. I have relatively minimal road race racing experience, but in all those years, with most of my riding on the road, I think 110 psi is max that I've ever pumped my tires (23mm).

Best reference I can give you is this Dylan Johnson/ Josh Poertner video which is highly relevant to this thread and worth watching in its entirety:
https://www.youtube.com/watch?v=ZuxUWFziuGI

I think this thread has established two things for me so far:
1 There isn't agreement that the VeloNews tests and the BRR tests are completely anti-correlated, so I need to do a spreadsheet on that and publish it first, before I do anything else.
2 Once it's understood that they're anti-correlated, nobody has any idea which test methodology is correct or why. The general consensus appears to be that they are both useful together, but of course this is impossible if they're anti-correlated.

@thumper88 A friend of mine actually had those quarq valves and got so disgusted with them blowing up mid ride he gave me the one he had left. I've never mounted it but it would make a useful reference monitor to compare to an accurate gauge. I purchased one that was externally verified by consumer reports so TBD.

On new tire technology, it's worth noting that it's out there - all Vittoria tires now come ready to shed graphene, a toxic and immortal nano-material:
https://link.springer.com/chapter/10.1007/398_2021_78
My new gravel bike came with Vittorias which I dismounted and left in the corner, trying to figure out if it's even ethical to sell them. Here in Washington state, a new tire additive killed all the salmon recently:
https://www.washington.edu/news/2020/12/03/tire-related-chemical-largely-responsible-for-adult-coho-salmon-deaths-in-urban-streams/
Can't wait to see what Vittorias are going to kill off but not sure I want to be part of it.
stu
646 posts
#71Feb 18, 2023, 12:52 AM
Thanks for the video. I particularly liked the comments about the hysteresis depending on speed.
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thumper88
198 posts
#72Feb 18, 2023, 6:40 AMedited
Almost everyone here who pays attention to tire stuff has seen that video and probably watched it a few times. And seen additional material from them on the topic. And read lab results from people like Anhalt those two built their thoughts on.
As someone who spent years analyzing complicated medical research, I can assure you Johnson knows his way around data, its stengths and weaknesses and what constitutes useful results, etc
These are two of the sharper thinkers on the topic and we’ve pretty much taken their results and thinking into account in the discussion here. Indeed, I talk to Dylan fairly often about tires and his thinking mirrors pretty much anything Ive said here.

OP, I appreciate this is all pretty exciting to someone who’s just started thinking about it for the first time, but I’d dial back the combativeness. You got a lot of good advice here. Just put it in the hopper and make your decisions. If you paid attention to the video you heard Portner and Dylan say exactly what several of us have: that BRR is a good tool, not perfect but def something to consult. You also heard Dylan say he consults Silca’s tire pressure tool before every race. These are both guys who I know for a fact have themselves tested and/or raced enough of the tires on the list to know what they’re doing and when they say they both consult and trust the list as a tool? I’d listen.
The tires in the opening illustration are NOT tires Dylan uses himself except perhaps at Croatan. They’re for illustration.
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John Z
174 posts
#73Feb 18, 2023, 10:18 AM
The most important take-away from the video is that generally speaking, regarding pressure it is better to err on the low side, something I mentioned above.
2
wheelmonkey
8 posts
#74Feb 18, 2023, 3:45 PM
[QUOTE username=thumper88 userid=5644110 postid=1334520259]
OP, I appreciate this is all pretty exciting to someone who’s just started thinking about it for the first time, but I’d dial back the combativeness. You got a lot of good advice here. /QUOTE]

I appreciate what you're saying and want you to know that any combativeness I've radiated here was unintentional. In my reply I cited a podcast as a source for "pros used to race at 150 psi and up", as someone else asked me for a reference on that and Poertner explicitly says this in his interview. I understand this podcast is old hat to many here and I shared it for the folks in this thread who like me are coming up to speed, not to try to counter anything you've said.

I understand that I'm getting a lot of wisdom here and I don't want to appear ungrateful.
I think an objective summary here is (please correct me if I get this wrong):
Velonews published an article with RR ratings done at WheelEnergy
Velonews published an elaborate criticism of BRR's testing methdology
Velonews ratings put the G-One R as the fastest tested large volume gravel tire
BRR ratings put the G-One R as one of the slowest large volume gravel tires ever tested
I need to find a way to integrate "fastest under test" and "nearly slowest under test" into a decision for what to race on this summer
I need to find a way to integrate the published methodology criticism from VeloNews into a decision
So far, I haven't learned enough to be able to integrate all this information into a decision, so I ordered some non-race tires and am hoping to defer the decision until weeks before first race
I'm not sure what to do except further statistical analysis or DIY testing, so that's my current plan (in that order).

Accepting all this data as good data makes a lot of sense. Imagine you were a head of household shopping for a family sedan and you had to integrate a 1-star safety rating and a 5-star safety rating for the same car into a purchasing decision. Imagine the 5-star lab had published an elaborate attack on the 1-star lab's testing methodology in the press. It's difficult. I hope you can empathize with how confusing that would be.

I want to assure you I am listening and learning. I just haven't been able to make a decision. Fortunately the stakes are low as Covid just put a huge dent in my Zwifting plans and I am probably going to suck out there regardless :-)
Thanks for sharing your experiences and information
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John Z
174 posts
#75Feb 19, 2023, 11:52 AMedited
I started a spreadsheet for a delta comparison between the VN and BRR data but gave up due to nomenclature confusions. In addition, I don't know if VN is testing with tubes or sealant (except as noted "latex tube"), and BRR data is now normalized to sealant-equivalent results.

Clearly, the WheelEnergy protocol will result in higher RR measurements, since its drum is rougher. To that, while its drum may very well better simulate a consistent rough surface like scarified pavement or cobbles, I am not 100% certain WheelEnergy's method provides and more meaningful data to make an selection.

The OP has problems with BRR, and I have problems with VN not including Continental, Tufo and even Rene Herse tires in their test. VN tested 24 tires, 5 of which are tubular tires. BRR has tested to date 66 gravel tires, none being tubular? Who in their right mind uses tubular gravel tires? Seems to me VN is trying to steer readers to a Challenge, Schwalbe or Panaracer Tire, not that these are bad tires. 13/24 (54%) of VN tire's tested are under 40mm wide; while only 27/66 (41%) of BRR's tested tires are under 40mm. So, while WheelEnergy's testing method may provide useful data. VN's selection of tires to test is abysmal and for me, makes the test data useless.

I may have said this before regarding G-One R "large volume" but there is possibly both a nomenclature issue and Schwalbe changed the compound, as the BRR test is from 2021. If your are worried about an outlier, pick another tire then. The second fastest large volume tire is not going to make a difference in your results, nor would the third, or fourth...
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Alagrav
18 posts
#76Feb 19, 2023, 4:01 PM
wheelmonkey wrote:

Best reference I can give you is this Dylan Johnson/ Josh Poertner video

Thanks for the video link. I've seen it.

But did you race with tire pressures approaching 200 psI? Or hear first hand from someone who did.

I'm not trying to be argumentative, I'm really curious if running pressures greater than 150 psi was much of a real thing. or instead it was something that old hands told newbies back in the 80s and 90s in order to mess with them. To me, the racing super high pressure claim seems more of an urban myth. Most tires had maximum pressure rating of 120-130 psi.

If I heard correct on the video, Josh Poertner claims to have been harping, for 13 years, about the inflection point where higher pressure begins to increase rolling resistance. But I've know about it longer than that. Here for instance is a discussion on a triathlon forum about tire pressure in 2003 (about as far back as the forum goes), and in the discussion several posters explain how bouncing from road bumps increases rolling resistance at too high pressures. There is even a reference to a unfinished article on the subject (but the link to that doesn't work). One of those posters, Superdave, is a long time bicycle industry guy. (Poertner by the way is a long time member/poster to that forum.) Superdave says he runs 85psi on 25 mm tires -- probably pretty close to what the silica calculator would say--and again this is 2003.

My point is that at least 20 years ago the myth of super high pressure was blown, and it was known that there is a point where higher pressure begins to increase rolling resistance.

But 20 years is about as far as I can go researching this question on internet forums. And I haven't kept any copies of the triathlon or cycling magazines I used to read in the 90s.

I wish I had thought of this yesterday, post race, while I was hanging around with some of the other sexagenarians (sounds dirty, but it means 60+ racing class).

Peace
1
Alagrav
18 posts
#77Mar 3, 2023, 8:47 PM
thumper88 wrote:
And just to show how muddy the water can get,

Speaking of muddy water, would you be willing to share tire recommendations for Mid South Gravel which is coming up on the 9th. I'm sure you know some years it can be super muddy. Some years dry. I'm guessing Terra Speed would be fine if dry, but what if it is muddy?
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thumper88
198 posts
#78Mar 4, 2023, 5:42 AM
Alagrav wrote:

Speaking of muddy water, would you be willing to share tire recommendations for Mid South Gravel which is coming up on the 9th. I'm sure you know some years it can be super muddy. Some years dry. I'm guessing Terra Speed would be fine if dry, but what if it is muddy?

First, def listen to someone else and hopefully people who have done it in a muddy year -- or better yet TWO years to compare -- will pipe up . I haven’t done Mid South and that’s pretty much the reason. I have a longer, early-season race that is much much closer and the idea of traveling a long way for a shorter race that is potentially going to be super muddy just doesn’t excite.
Def need someone to weigh in here about what the mud there is like, in detail --- typically how many miles of it, how deep it is, how clingy and what has worked for them.
Mud varies quite a lot and that would weigh on tire choice. Ive got a set of the pretty narrow and knobby panaracer mud tires but cannot imagine any circumstances in which I’d use them. They’re dead slowand usually even a pretty muddy race is mostly on harder terrain and pavement.
And in truly serious mud I haven’t noticed much difference in tread vs no tread except maybe tread can hold more mud.
One attribute that does help is going a size down from whatever you might normally use. In theory in SOME kinds of mud that might help the tire punch though to harder ground below. But probably a bigger thing, going down in size a little def has helped me with clearance when mud does build some.
The stuff at unbound this past year, no tire would work. None. it would build up enough in 10 feet to stop the bike from rolling and extra clearance would have helped zero.
Anyway, hoping we have some mid south veterans here to bring you something more useful and specific.
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